US3510738A - Proportional controller with nonlinear proportional band width control - Google Patents

Proportional controller with nonlinear proportional band width control Download PDF

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Publication number
US3510738A
US3510738A US562745A US3510738DA US3510738A US 3510738 A US3510738 A US 3510738A US 562745 A US562745 A US 562745A US 3510738D A US3510738D A US 3510738DA US 3510738 A US3510738 A US 3510738A
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United States
Prior art keywords
proportional
controller
band width
variable
control element
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Expired - Lifetime
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US562745A
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English (en)
Inventor
Kristian Iversen
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Danfoss AS
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Danfoss AS
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    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
    • G05B5/00—Anti-hunting arrangements
    • G05B5/01—Anti-hunting arrangements electric
    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05D—SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES
    • G05D23/00—Control of temperature
    • G05D23/19—Control of temperature characterised by the use of electric means
    • G05D23/1906—Control of temperature characterised by the use of electric means using an analogue comparing device
    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05D—SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES
    • G05D23/00—Control of temperature
    • G05D23/19—Control of temperature characterised by the use of electric means
    • G05D23/1927—Control of temperature characterised by the use of electric means using a plurality of sensors
    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05D—SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES
    • G05D23/00—Control of temperature
    • G05D23/19—Control of temperature characterised by the use of electric means
    • G05D23/20—Control of temperature characterised by the use of electric means with sensing elements having variation of electric or magnetic properties with change of temperature
    • G05D23/24—Control of temperature characterised by the use of electric means with sensing elements having variation of electric or magnetic properties with change of temperature the sensing element having a resistance varying with temperature, e.g. a thermistor
    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05D—SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES
    • G05D23/00—Control of temperature
    • G05D23/19—Control of temperature characterised by the use of electric means
    • G05D23/30—Automatic controllers with an auxiliary heating device affecting the sensing element, e.g. for anticipating change of temperature
    • G05D23/303—Automatic controllers with an auxiliary heating device affecting the sensing element, e.g. for anticipating change of temperature using a sensing element having a resistance varying with temperature, e.g. thermistor

Definitions

  • Proportional-position action in controllers is well known.
  • Proportional-position controllers have a serious limitation of offset in that they have an inability to return the controlled variable to its set point after a load change has caused a deviation.
  • simple proportional control has a limitation in that there is a change of control point with load.
  • proportional-integral controllers are used. The integral action, however, results in decreased stability and dead control.
  • Proportional controller adjustment is simply a matter of setting the proportional band wide enough for stability under abnormal as well as normal process conditions. Too narrow a band causes cycling; too wide; dead control.
  • a feature of the controller in accordance with the invention, is the provision of means for gradually reducing the proportional band during intervals in which the final control element, of a control loop, is not being actuated by the controller and the band Width is increased during the intervals in which the final control element is operatmg.
  • a proportional controller for controlling a final control element manipulating a manipulated variable.
  • Automatic controller actuating means apply a control output to the final control element for manipulating the manipulated variable.
  • Measuring means are connected in the controller to measure a controlled variable and means are provided to establish a set point of the controlled variable. It being understood that the set point is representative of a value obtaining when the manipulated variable has a selected value.
  • the controller comprises means to apply to the controller actuating means therein an actuating signal corresponding toa deviation of the controlled variable from the set point effective to cause the actuating means to cause the final control element to manipulate the manipulated variable to the selected value thereof.
  • the improved controller of the invention comprises a proportional band width control means cooperative with the actuating and measuring means in the controller to establish a proportional band width of operation of the final element adjustably varying in time and effective to maintain the proportional band width sufficiently wide to maintain the controller stable and at least decreasing the proportional band width incrementally.
  • the new and improved controller provides simple proportional control with all its advantages while eliminating offset.
  • the manipulated variable is controlled with stability and without dead control. Not until the final control element has found its rest position and an actuating signal to the controller is not applied is the band width of the proportional band gradually diminished. The diminishing or reducing of the band width reduces the offset.
  • the proportional band is increased. During this interval the control element is being actuated and increasing of the band width thereby maintains stability of the controller. Since the narrowing of the proportional band width takes place during progressively diminishing intervals of time, the stability of the controller is unaffected and its porportional action characteristics are unaffected.
  • the new and improved controller comprises circuitry having a variable resistance means therein capable of varying in resistance in a direction for reducing the proportional band width during intervals in which the final control element is not being actuated for controlling the manipulated variable and other variable resistance means, namely a transistor, that increases the band width during operation of the final control element for maintaining stability of the controller.
  • a shunt circuit 1 is provided with terminals 2, 3, for receiving a direct current voltage to establish a reference input.
  • Measuring means,- comprising a resistor 4 is provided for sensing a controlled variable, for example temperature, and is connected in series with a variable resistor 5 for establishing a set point of the controlled variable.
  • the resistor 7 is a voltage-dividing, feedback potentiometer having a movable contact 9.
  • a variable resistor 10 for setting the proportional band or throttling range of a final control element, for example a valve, not shown.
  • the proportional band is, of course, the change of controlled variable necessary to move the final control element through its full stroke.
  • connections are made between the measuring means or measuring resistor 4 and the variable resistor 5 for taking off a voltage or signal to an amplifier 12 connected to the contact 9.
  • the output of the amplifier is applied to operating coils 13, 14 of relay means having movable contacts 15, 16 associated with respective operating coils 13, 14.
  • the contacts are normally in the position illustrated in the drawing when the final control element is not being actuated and are moved to fixed contacts for applying an alternating current to a split-phase, reversible induction motor 17 having, for example, a capacitance for starting.
  • the motor is connected to an alternating current power source at terminals 18.
  • the motor 17 is thus reversibly driven in a direction for driving the final control element, for example a valve, manipulating the manipulated variable, for example flow of a medium, to which the control variable, for example temperature, is related.
  • the adjusting movement of the motor 17 takes place within the proportional band set by the shunt switch circuit 1.
  • the circuit switch 1 applies a signal to a correct one of the relay coils 13, 14 actuating the correct movable contacts of the relay means to a position in which the respective contact is moved to a position for applying an alternating voltage to the motor 17.
  • the motor has caused the final control element to manipulate the manipulated variable to the selected level, it comes to a standstill and the contacts return to the position illustrated completing a circuit for varying the resistance of a transistor 20 and a variable resistor 21 by means of a heating resistor 22 placed in circuit with the power source 18.
  • the resistor 21 is connected to the transistor 20 and the potentiometer and receives a DC. input from the direct current power source, not shown, through the terminals 2, 3 and has the characteristic of decreasing in resistance when heated. As the resistance of the temperature-dependent resistor 21 decreases, an increased base current flows through the transistor 21 and the internal resistance of the emitter-collector path of this transistor decreases. This results in a diminishing or reduction of the proportional band width of the proportional hand during intervals in which the actuating signal is not being applied to the motor 17 for moving the final control element. This interval corresponds to the interval during which the final control element is at rest and substantially during which the manipulated variable has not deviated enough from its selected value to cause the controller to effect its corrective action.
  • the motor 17 is again energized when one of the relay coils 13, 14 is reactivated.
  • the resistor 22 is deenergized so that the variable resistor 21 cools somewhat and thereby increases the band width until conformity is obtained between the existing value of the manipulated variable and its selected value. This motor operation is repeated several times until the band width is quite narrow and the oifset or deviation is substantially negligible.
  • variable resistor 21 may reach an end-temperature under control of the heating resistor 22. This end-temperature is representative of the narrowest proportional band width. If now the measuring device 4 senses a temperature deviation, the motor 17 begins to operate. During the period of operation of the motor, the temperature-dependent resistor 21 cools. The cooling is more intense the longer the motor 17 operates. Consequently, the band width of the proportional band extends or widens more the longer the motor 17 operates. That is to say, the larger the temperature deviation measured by the measuring means 4 is the greater the band width is widened. This condition maintains the stability of the controller and the sensitivity thereof so that the controller is optimally adapted to control manipulated variable or load changes.
  • a proportional controller for controlling a final control element manipulating a manipulated variable
  • automatic actuating means applying a control output to said final control element for manipulating said variable
  • measuring means measuring a controlled variable
  • means under control of said measuring meansto apply to said actuating means an actuating signal corresponding to a deviation of said controlled variable from said set point eifective to cause said actuating means to cause said final control element to manipulate said manipulated variable to said selected value
  • nonlinear proportional band width control means connected in said controller cooperative with said actuating means and said measuring means to establish a proportional band width of operation of said final control element adjustably varying in time effective by increasing said proportional band when said actuating means is not actuating said final control element to maintain said proportional band width sufficiently wide to maintain said controller stable and decreasing said proportional band Width at least incremently when said actuating means is actuating
  • said nonlinear proportional band width control means comprises means to decrease said proportional band width during intervals in which said manipulated variable is substantially at said selected value and said final element is thereby at rest and not manipulating said manipulated variable.
  • said nonlinear proportional band width control means comprises means to increase the band width proportionately to the time'said final control element is manipulating said manipulated variable.
  • nonlinear proportional band width control means compises means to nonlinearly increase said band width during the time said output is applied to said final control element.
  • said nonlinear proportional band width conmeans comprises an electrically energized circuit having a variable resistance means effective automatically to alter said proportional band width in a direction decreasing said proportional band width incrementally proportionally to and during an interval of application of said output to said final control element to narrow said proportional band and offset corresponding to a deviation between said selected value of said manipulated variable and a value of said manipulated value established by said final control means and effective to increase the proportional band width during intervals of nonapplication of said control output to said final control elementto maintain said controller substantially stable.
  • variable resistance means comprises a resistor in said circuit having the characteristic of reducing in resistance when heated, heating means heating said resistor during said intervals of non-application of said output to said final control element.
  • variable resistnce means comprise a tran- Referenc es Cited control el me t, 2,663,832 12/ 1953 McDonald 61: a1.
  • 318-29 XR 9.
  • said actuating means comprises a split-phase, 5 353911315 7/1968 Schwartzenberg 313448 XR reversible induction motor, means to apply an h t- 3,391,316 7/ 1963 88 318-18 ing current to said motor
  • said proportional band Width BENJAMIN DOBECK Primary Examiner control means comprising means under control of said measuring means to connect the last-mentioned means 10 to said motor and to said heating means alternately.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Automation & Control Theory (AREA)
  • Feedback Control In General (AREA)
  • Electrical Control Of Air Or Fuel Supplied To Internal-Combustion Engine (AREA)
  • Control Of Temperature (AREA)
  • Laminated Bodies (AREA)
  • Reinforced Plastic Materials (AREA)
US562745A 1965-07-13 1966-07-05 Proportional controller with nonlinear proportional band width control Expired - Lifetime US3510738A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
DED0047719 1965-07-13

Publications (1)

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US3510738A true US3510738A (en) 1970-05-05

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Country Status (10)

Country Link
US (1) US3510738A (ja)
AT (1) AT267683B (ja)
BE (1) BE683169A (ja)
CH (1) CH448579A (ja)
DE (1) DE1523478B2 (ja)
FR (1) FR1486062A (ja)
GB (1) GB1111747A (ja)
NL (1) NL6609712A (ja)
NO (1) NO120765B (ja)
SE (1) SE322571B (ja)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3704404A (en) * 1969-12-17 1972-11-28 Danfoss As Regulating means
US3731178A (en) * 1970-02-10 1973-05-01 Zellweger Uster Ag Process and apparatus for effecting control over control systems for non-linear control procedures
US3957200A (en) * 1975-02-20 1976-05-18 Johnson, Controls, Inc. Humidity controller
US4770065A (en) * 1985-07-22 1988-09-13 Reliance Electric Company Variable speed drive
EP1146405A2 (de) * 2000-04-12 2001-10-17 Bayerische Motoren Werke Aktiengesellschaft Regelverfahren

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2456599C2 (de) * 1974-11-29 1983-11-24 Vysoká škola strojní a textilní, 46117 Liberec Verfahren und Vorrichtung zur Stabilisierung eines Regelkreises
US4201061A (en) * 1978-03-22 1980-05-06 Carrier Corporation Automatic chilled water setpoint temperature control

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2663832A (en) * 1952-10-01 1953-12-22 Cook Electric Co Multiple mode closed-cycle control system
US2694169A (en) * 1950-05-05 1954-11-09 Honeywell Regulator Co Electric proportioning control apparatus with automatic reset
US3391316A (en) * 1964-10-20 1968-07-02 Leeds & Northrup Co Process controller in which proportional and reset actions are adaptively modified by process load
US3391315A (en) * 1964-10-20 1968-07-02 Leeds & Northrup Co Process controller in which rate action is adaptively modified by process load using a pulse-width modulator

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2694169A (en) * 1950-05-05 1954-11-09 Honeywell Regulator Co Electric proportioning control apparatus with automatic reset
US2663832A (en) * 1952-10-01 1953-12-22 Cook Electric Co Multiple mode closed-cycle control system
US3391316A (en) * 1964-10-20 1968-07-02 Leeds & Northrup Co Process controller in which proportional and reset actions are adaptively modified by process load
US3391315A (en) * 1964-10-20 1968-07-02 Leeds & Northrup Co Process controller in which rate action is adaptively modified by process load using a pulse-width modulator

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3704404A (en) * 1969-12-17 1972-11-28 Danfoss As Regulating means
US3731178A (en) * 1970-02-10 1973-05-01 Zellweger Uster Ag Process and apparatus for effecting control over control systems for non-linear control procedures
US3957200A (en) * 1975-02-20 1976-05-18 Johnson, Controls, Inc. Humidity controller
US4770065A (en) * 1985-07-22 1988-09-13 Reliance Electric Company Variable speed drive
EP1146405A2 (de) * 2000-04-12 2001-10-17 Bayerische Motoren Werke Aktiengesellschaft Regelverfahren
EP1146405A3 (de) * 2000-04-12 2002-03-06 Bayerische Motoren Werke Aktiengesellschaft Regelverfahren
US6541934B1 (en) 2000-04-12 2003-04-01 Bayerische Motoren Werke Aktiengesellschaft Electric drive control

Also Published As

Publication number Publication date
NL6609712A (ja) 1967-01-16
NO120765B (ja) 1970-11-30
FR1486062A (fr) 1967-06-23
DE1523478A1 (de) 1969-05-14
BE683169A (ja) 1966-12-01
SE322571B (ja) 1970-04-13
AT267683B (de) 1969-01-10
CH448579A (de) 1967-12-15
DE1523478B2 (de) 1973-08-16
GB1111747A (en) 1968-05-01

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